Please I need help Thanks 2 Identical twins are produced fro

Please I need help. Thanks

2. Identical twins are produced from the same sperm and egg (which splits after the first mitotic division), whereas fraternal twins are produced from separate sperm and separate egg cells. If two parents with brown eyes (a dominant trait) produce one twin boy with blue eyes, what are the following probabilities? A. If the other twin is identical, he will have blue eyes. Ba lf the other twin is fraternal, he or she will have blue eyes. C. If the other twin is fraternal, he or she will transmit the blue eye allele his or her offspring D. The parents are both heterozygotes

Solution

As the brown eye colour is dominant, that means the parents are Bb and Bb (denoting the alleles of the chromosomes)

B- dominant brown (brown colour expressed when even one allele \"B\" is present)

b- recessive blue (to express blue colour in eye, both alleles on the chromosome should be \"bb\")

Now according to question as one twin boy has blue eyes, the parents have to be carriers of blue (Bb and Bb). If they both or even one of them was all dominant \"BB\", no child would have blue eyes).

2A) Probability of other twin having blue eyes = 1 (or 100% as both identical twins are same in all respects)

2B) Fraternal child is like any other child altogether that the parent may have with no relation with identical twin. Therefore probability for fraternal kid to have blue eyes (bb) will be = 1/4

2C) Fraternal kid will transmit blue eye allele to his her offspring: To transmit the blue eye colour, the fraternal kid has to be (Bb). therefore the probiliby is 2/4 or 1/2.

2D) Th eparents are both heterozygotes (means they both are Bb). 100% chance or probability is 1 (It is certain). Otherwise they cannot have a kid with blue eyes until both parents carry the recessive blue eye allele.

	Father (B)	Father (b)
Mother (B)	Child (BB)	Child (bB)
Mother (b)	Child (Bb)	Child (bb)